There are two common methods for blending large amounts of ingredients into the desired mixture. One method is batch mixing. Batch mixing is the process of sequentially adding the ingredients together in their proper proportions and then agitating the ingredients to produce a mixture of uniform ingredient consistency. This is typically done by weighing into a scale. A well known example of batch mixing is a concrete mixing truck. However, batch mixing is time intensive and requires large, expensive equipment. A second method is volumetric blending. Volumetric blending involves sequentially or simultaneously adding ingredients to central container according to the desired proportions of each ingredient such that, at the end of the mixing, the central container holds a homogeneous mixture. Compared to batch mixing, volumetric blending is less expensive, less time intensive and does not require as much physical area as batch mixing. However, calibration of a volumetric blending equipment must be accurate to ensure that the correct proportion of each ingredient is added to the mixture.
One method of calibration is disclosed in U.S. Pat. No. 4,667,503, titled "Method of Calibrating Volumetric Metering and Blending Device", issued May 26, 1987 to Bruce J. Loos and assigned to Monarch Specialty Systems, Inc. of Ossian, Ind. The Loos patent discloses calibration of volumetric continuous blending equipment by calculating the ratio of weight of each ingredient dispensed to the movement of dispensing augers for a small sample of the total mixture. A quantity of each ingredient is dispensed by the movement of dispensing augers to a weighing hopper until the weighing hopper measures a predetermined weight for each ingredient. The predetermined weight is the exact weight ratio of the ingredient in the desired mixture. Once this predetermined weight is reached, the equipment records the number of turns of the dispensing auger. The equipment is then calibrated by calculating the ratio of ingredient weight for each turn of the dispensing auger. Once the calibration is complete for each ingredient, the equipment then monitors the speed of all the dispensing augers as they feed into a common hopper to ensure each ingredient is added to the hopper mixture in the desired proportions.
The problem with the above method of calibration is that the equipment must be calibrated for each ingredient in each new mixture. This requires a sample run of each ingredient at the ratio of the new mixture and is both time and labor intensive. A calibration method that does not require a mixture sample run would be greatly appreciated.